package com.example.mylibrary.utils;

import android.text.TextUtils;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.spec.RSAPublicKeySpec;

import javax.crypto.Cipher;

/**
 * Created by Hejx on 2017/9/15.
 * 编码工具
 */
public class CodeUtil {

    // MD5加密
    private static final String MD5 = "MD5";
    // RSA加密
    private static final String RSA = "RSA";
    // RSA加密参数
    private static final String RSA_NONE_PKCS1 = "RSA/None/PKCS1Padding";

    /**
     * RSA加密
     */
    public static String encryptByRSA(String source, String modulus, String exponent) {
        byte[] bytes = new byte[0];
        try {
            // 得到公钥
            byte[] modulusBytes = Base64.decode(modulus);
            byte[] exponentBytes = Base64.decode(exponent);

            BigInteger bigIntModulus = new BigInteger(1, modulusBytes);
            BigInteger bigIntExponent = new BigInteger(1, exponentBytes);

            RSAPublicKeySpec keySpec = new RSAPublicKeySpec(bigIntModulus, bigIntExponent);
            KeyFactory kf = KeyFactory.getInstance(RSA);
            PublicKey keyPublic = kf.generatePublic(keySpec);

            // 加密数据
            Cipher cp = Cipher.getInstance(RSA_NONE_PKCS1);
            cp.init(Cipher.ENCRYPT_MODE, keyPublic);
            bytes = cp.doFinal(source.getBytes("utf-8"));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return Base64.encode(bytes);
    }

    /**
     * 使用MD5加密
     */
    public static String encryptByMD5(String source) {
        String result = "";
        if (!TextUtils.isEmpty(source)) {
            try {
                MessageDigest md5 = MessageDigest.getInstance(MD5);
                byte[] bytes = md5.digest(source.getBytes());
                for (byte b : bytes) {
                    String temp = Integer.toHexString(b & 0xff);
                    if (temp.length() == 1) {
                        temp = "0" + temp;
                    }
                    result += temp;
                }
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
            }
        }
        return result;
    }

    @SuppressWarnings("WeakerAccess")
    public static class Base64 {

        private static char[] base64EncodeChars = new char[]{
                'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
                'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
                'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
                'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};

        private static byte[] base64DecodeChars = new byte[]{
                -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
                -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
                -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
                -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
                17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30,
                31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
                51, -1, -1, -1, -1, -1};

        public static String encode(byte[] data) {
            StringBuilder sb = new StringBuilder();
            int len = data.length;
            int i = 0;
            int b1, b2, b3;
            while (i < len) {
                b1 = data[i++] & 0xff;
                if (i == len) {
                    sb.append(base64EncodeChars[b1 >>> 2]);
                    sb.append(base64EncodeChars[(b1 & 0x3) << 4]);
                    sb.append("==");
                    break;
                }
                b2 = data[i++] & 0xff;
                if (i == len) {
                    sb.append(base64EncodeChars[b1 >>> 2]);
                    sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
                    sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);
                    sb.append("=");
                    break;
                }
                b3 = data[i++] & 0xff;
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
                sb.append(base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]);
                sb.append(base64EncodeChars[b3 & 0x3f]);
            }
            return sb.toString();
        }

        public static byte[] decode(String str) {
            try {
                return decodePrivate(str);
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
                return new byte[]{};
            }
        }

        private static byte[] decodePrivate(String str) throws UnsupportedEncodingException {
            StringBuilder sb = new StringBuilder();
            byte[] data;
            data = str.getBytes("US-ASCII");
            int len = data.length;
            int i = 0;
            int b1, b2, b3, b4;
            while (i < len) {
                do {
                    b1 = base64DecodeChars[data[i++]];
                } while (i < len && b1 == -1);
                if (b1 == -1) {
                    break;
                }
                do {
                    b2 = base64DecodeChars[data[i++]];
                } while (i < len && b2 == -1);
                if (b2 == -1) {
                    break;
                }
                sb.append((char) ((b1 << 2) | ((b2 & 0x30) >>> 4)));
                do {
                    b3 = data[i++];
                    if (b3 == 61) {
                        return sb.toString().getBytes("iso8859-1");
                    }
                    b3 = base64DecodeChars[b3];
                } while (i < len && b3 == -1);
                if (b3 == -1) {
                    break;
                }
                sb.append((char) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));
                do {
                    b4 = data[i++];
                    if (b4 == 61) {
                        return sb.toString().getBytes("iso8859-1");
                    }
                    b4 = base64DecodeChars[b4];
                } while (i < len && b4 == -1);
                if (b4 == -1) {
                    break;
                }
                sb.append((char) (((b3 & 0x03) << 6) | b4));
            }
            return sb.toString().getBytes("iso8859-1");
        }
    }
}
